25 February 2019 to 1 March 2019
Budker INP
Asia/Novosibirsk timezone

Meson spectroscopy at VES and COMPASS

27 Feb 2019, 17:50
20m
Conference room

Conference room

Invited Oral Spectroscopy of light and heavy quarks e+e– annihilation and gamma–gamma physics

Speaker

Dr Dmitry Ryabchikov (Institute for High Energy Physics)

Description

Diffractive production of $\pi^+\pi^-\pi^-$ and $\pi^-\pi^0\pi^0$ final states are subjects of comprehensive studies performed recently by VES and COMPASS experiments. The $3\pi$ states are produced at VES by 29 GeV/c $\pi^-$ beam on Be target ( $87x10^6$ $\pi^+\pi^-\pi^-$ events and $32x10^6$ $\pi^-\pi^0\pi^0$ events analyzed at 0 < t' < 1 GeV/c$^2$). At COMPASS $3\pi$ states are produced by 160 GeV/c $\pi^-$ beam impinging on liquid hydrogen target ( 50x10$^6$ $\pi^+\pi^-\pi^-$ events and $3.5x10^6$ $\pi^-\pi^0\pi^0$ events analyzed at 0.1 < t' < 1 GeV/c$^2$). The COMPASS collaboration pioneered the application of novel methods of partial-wave analysis: mass-independent PWA in multiple (m,t')-cells, mass-dependent analysis performed at-once for density matrices measured in all t' regions, the analysis with free shapes of $\pi^+\pi^-$ isobars. The COMPASS observed new narrow state: a_1(1420). The VES has leading world statistics of $\pi^+\pi^-\pi^-$ and $\pi^-\pi^0\pi^0$ events, compatible in two final states. This makes perspective the comparison of isospin relations between two states, using both: PWA with established shapes of isobars and PWA with freed $\pi\pi$ isobars.

Primary author

Dr Dmitry Ryabchikov (Institute for High Energy Physics)

Presentation Materials

Peer reviewing

Paper